KVM: SVM: Remove remaining occurences of rdtscll

This patch replaces them with native_read_tsc() which can
also be used in expressions and saves a variable on the
stack in this case.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>